How late is too late for nitrogen top up?
Canola with higher yield potential could need more nitrogen. And excess moisture can increase nitrogen losses.
Nitrogen top dress before the five-leaf stage gets nitrogen into the root zone before peak uptake. Later applications could still help. Agriculture and Agri-Food Canada research out of Indian Head, Saskatchewan showed a yield benefit from nitrogen top up as late as five to 10 per cent flower.
A nitrogen top up could extend the vegetative period and delay maturity, but probably not by much. Sally Vail with Agriculture and Agri-Food Canada, Jeff Schoenau with the Univeristy of Saskatchewan and Mario Tenuta at the University of Manitoba each suggest, based on research and in-field experience, a minimal delay in canola maturity, even with a later-than-recommended top up.
How about sulphur? Schoenau reports patchy sulphur deficiency in fields, especially sandy fields, in southern Saskatchewan that received four or more inches of rain in one shot earlier in season. He says late application of ammonium sulphate can help. Tips to apply nitrogen and sulphur in season
